As a process for producing optically active 3-hydroxy-3-phenylpropanenitrile, there are known 1) a process for deriving it from an optically active precursor substance (Patent Documents 1 and 2); 2) a process for optically resolving racemic 3-hydroxy-3-phenylpropanenitrile with a hydrolyzing enzyme such as lipase (Patent Document 3, Non-Patent Document 2); 3) a process for condensing benzaldehyde and acetonitrile in the presence of an asymmetric ligand and a metallic catalyst (Non-patent document 3); 4) a process for reducing an carbonyl group of 3-oxo-3-phenylpropanenitrile in the presence of an asymmetric ligand or an asymmetric catalyst (Patent Document 4 and Non-Patent Document 4); and 5) a process for reducing an carbonyl group of 3-oxo-3-phenylpropanenitrile by use of a microorganism (Non-Patent Documents 5 and 6).    Non-Patent Document 1: Bulletin of the Korean Chemical Society, 23, 1693 (2002)    Non-Patent Document 2: Advanced Synthesis & Catalysis, 344, 947 (2002)    Non-Patent Document 3: Organic Letters, 5, 3147 (2003)    Non-Patent Document 4: Tetrahedron: Asymmetry, 3, 677 (1992)    Non-Patent Document 5: Tetrahedron: Asymmetry, 11, 3693 (2000)    Non-Patent Document 6: Organic Letters, 1, 1879 (1999)    Patent Document 1: US. Patent Application Laid-Open No. 2004/110985    Patent Document 2: Japanese Patent Application Laid-Open No. 5-92946    Patent Document 3: National Publication of International Patent Application No. 2004-520039    Patent Document 4: Japanese Patent Application Laid-Open No. 2003-201269